A spring is attached to a block, mass m, on a frictionless ramp. Let be the angle the plane makes with the horizontal. Assume the spring has unstreched length t and constant k.

1) establish the forces acting on the block. I got normal reation, weight and the restoring force.

2) Find L,the length the spring streches to hold the block in equlibrium. I got so by hooke's law but the answer said I needed to add t. Can anyone explain why?

3)show the mechanincal energy of the block is given by . Where x=the displacement measured up the slopeand chosen such that x=0 when l=t

I know that E=PE +KE but don't know how to obtain the equation.

Thanks